What is the burden that falls upon me if I take out an interest-based loan from someone who is the only resort to relieve my financial distress?

This transaction is usurious (riba-based), and all parties involved are sinful and cursed, based on the Prophet Muhammad's (peace be upon him) saying: "Allah has cursed the one who consumes usury, the one who gives it, the one who records it, and the two witnesses to it. And he said: They are all alike."

Do not proceed with this transaction. Fear Allah and rely on Him alone; for whoever does so, Allah will grant them relief and a way out, and provide for them from where they do not expect, as mentioned in Surah At-Talaq.

The usurer exploited your need by demanding a 20% increase for one year, which is an exorbitant exploitation that could lead to an accumulation of debts and sin. Close this door, seek Allah's help, and consult experts.